In our prior proposed invention (U.S. patent application Ser. No. 14/462,320) for stereotactically guiding an invasive device to reach a tissue object under ultrasonographic visualization, we presented an apparatus that comprises a stereotactic positioning system, a powered propulsion system of an invasive device and a non-reusable invasive device. The apparatus provides in-process visualization of insertion procedures, which uses a trigonometric principle for coordinated angulation of an invasive device with movement of a linear positioning pointer in parallel with a transverse axis of a proximal end of an ultrasound transducer. The linear pointer is a component of an electromagnetic galvanometer-type positioning device that is located in between of the proximal end of the ultrasound transducer and a tissue object under evaluation. The linear pointer indicates a location of a tissue object by a linear shadow line emanating from the ultrasound transducer through the object, distinguished readily from surrounding tissue images. The linear shadow line is produced by the linear pointer blocking a portion of transmissible ultrasound waves generated by the ultrasound transducer toward a tissue object.
An electromagnetic galvanometer-type device comprises a set of electromagnetic windings circumferentially surrounding a pivoting wire core and a linear pointer connected to the pivoting wire core. Upon varying range of electric voltage, current or resistance applied to the electromagnetic galvanometer-type device, the device radially moves a linear pointer as the pivoting wire core rotates inside the electromagnetic windings. One issue of the radial movement of the linear pointer is that it produces oblique presentations to a portion of a linear axis of an ultrasound transducer array. As the majority of ultrasonographic images are generated by volume averaging methods, the oblique placement of the linear pointer in relation to a linear axis of an ultrasound transducer array may limit production of an accurate linear shadow line in an ultrasonographic field. This could produce ultrasonographic artifacts such as comet tail artifacts or side lobe artifacts, which may affect quality of imaging of the linear shadow line adversely.
Trigonometric angulation of an invasive device requires an apex about which the invasive device pivots, and a pivoting means. In our prior proposed invention, a rack and pinion assembly was proposed for pivoting the invasive device. A part of the rack and pinion was configured to be housed inside an ultrasound transducer enclosure. For maintenance of sterility of the apparatus, any opening into a main body of an apparatus increases a risk of contamination of the apparatus by biologic materials and microbial organisms. A sealed-off configuration of an apparatus may reduce chances of contamination of the apparatus and facilitates sterilization of the apparatus without damaging sensitive instruments inside. The sealing-off of the apparatus while allowing unimpeded pivoting of the invasive device about the apex of a trigonometric configuration of the apparatus can be achieved if the pivoting means is isolated from internal components of the apparatus and connected directly to the trigonometric apex for pivoting movements. This configuration obviates a need of placement of a separate pivoting mechanism such as the rack and pinion inside the ultrasound transducer enclosure.